un-dedicating a line to a dialer

[alt%aids-unix at sri-unix.UUCP]

From:  Howard Alt <alt at aids-unix>

Hmmm, it seems to me that a short suid root program that:
1) looks in utmp for someone logged in
2) changes the 1 to a 0 in /etc/ttys
3) sends a HUP signal to init
and another program that:
1) changes the 0 to a 1 in /etc/ttys
2) sends a HUP signal to init

you could call these enable and disable, and make them have a tty
as an argument.  You could even have it log enables and disables,
and check a list of ttys that it is ok to disable.  

uucico could then do a system("disable ttyd0"); to make it a dialout,
and a system("enable ttyd0); to make it a normal dialin again.
Does this do the same thing you were talking about, or does it
miss a case that your method catches?  The problem I can think of
is:  Somone just calls up, types thier login name and password
and the trash appears on thier screen.  uucico decided to call 
out just before thier name was entered in utmp, and after they 
dialed up.  Does your method keep this from happening?

				Howard.